You must be familiar with the long wait for hot water: You turn on a hot-water faucet and have to wait a full two minutes for the hot water to arrive. It is such a bad feeling while you are standing in cold and waiting for showering in freezing winter.

Several factors have conspired to make this problem worse when your houses are bigger, you’re installing more fixtures and appliances that use hot water, and the plumbing code is mandating larger-diameter pipes. To top it all off, new low-flow fixtures ensure that wait times are longer than ever.

If you live in a compact house and the water heater is located in the center of the basement, you may not have this problem. However, if you live in a stretched-out single-story home and the water heater is located in an attached garage, your bathroom may be 15m away from the water heater—a layout that basically guarantees a long wait.

How to solve the problem?

You can reduce your wait time for hot water in several ways. The first step is to insulate all your hot-water pipes. The second step is to reduce the diameter of the pipe from the water heater to the fixture. Compared to the time it takes hot water to arrive in 3⁄8-in.-dia. pipe at a given flow rate, it takes roughly 1-1⁄2 times as long in 1⁄2-in.-dia. pipe, three times as long in 3⁄4-in.-dia. pipe, and six times as long in 1-in.-dia. pipe. (3⁄8-in. tubing can be used to serve a single lavatory, while 1⁄2-in. tubing can serve a single shower.)

Another possible solution is installing a second water heater closer to the distant fixtures. if you don’t relish the thought of having two water heaters, you may want to install a pump to circulate hot water from your water heater to your most distant fixture. A well-designed hot-water circulation system will save energy, save water, and make your life a little more convenient.

A hot-water closed loop uses a small pump to circulate hot water between a water heater and a distant bathroom or kitchen. There are two types of circulation systems: Trunk-and-branch system and home-run system.

Trunk-and-branch system

The supply pipes in most older homes follow a trunk-and-branch arrangement rather than a home-run arrangement. In a trunk-and-branch system, a large diameter trunk pipe runs from the water heater to a remote bathroom. At that point, smaller pipes branch off to serve the lavatory, the shower, and (perhaps) the washing machine.

A hot-water circulation system with a demand-controlled pump can save both water and energy. These systems work best in older homes with trunk-and-branch plumbing layouts. In retrofit installations, the circulation pump uses the cold-water supply line as a temporary hot-water return line.

Home-run system

Home-run supply line is a system with separate cold and hot lines connecting each fixture to a central manifold near the water heater.

In a new house, a hot-water circulation system usually includes a dedicated return line connecting the most remote fixture with a pump near the water heater.

Efficient design tips for central heating

If you’re designing a new home, you’re in luck. Obey the following principles, and you can probably prevent the dreaded long wait for hot water.

• If possible, group your kitchen and all your bathrooms near each other, either back-to-back or stacked on top of each other. This creates a plumbing core that keeps pipe runs short.
• Install your water heater in a central location near the plumbing core.
• If your design includes a remote bathroom far from the water heater, consider installing a second heater to serve the remote fixtures.
• Install a home-run piping system connected to a central manifold. The manifold should be located near the water heater.
• Insulate all hot-water pipes.